Letterpress printing makeready



' March 4, 1958 J. B. GERGEN ET AL LETTERPRESS PRINTING MAKEREADY FiledApril 2, 1956 Aime/v26 I most popular.

United States Patent O 2,825,282 LETTERPRESS PRINTINGMAKEREADY James B.Gergen, West St. Paul, and Thomas G. Wartman, St. Paul, Minn., assignorsto Minnesota Mining & Manufacturing Company, St. Paul, Minn, a corpora-Thisinvention relates to the art of makeready especially as related toletterpress printing, to novel makeready methods and constructions, andto novel sheet material applicable thereto.

This application is a continuation-in-part of our application filedAugust 25, 1954, Serial No. 452,206, now abandoned.

I In letterpress printing, including flat-bed as well as rotary pressprinting, anirnpression cylinder or platen is commonly used to press a'sheet, usually paper, against the inked face (e. g., figures, designs,type, pictures, etc.) of a printing form. The face or image of. theprinting form (i. e., the surface of raised printing elements) isthereby printed upon the sheet.

Many different types or styles of apparatusmay be used inthis printingoperation. Printing forms may be mounted so as to rest upon-wood,honeycomb, or other types of bases. Impression cylinders or platens maybe wrapped with several layers of packing materials, such as papers,cloths, draw sheets, etc. A suitable, but not necessarily exact, pitchor printing line is maintained for the operation. In describing thisinvention, all illustrations are taken with respect to flat-bed pressprinting using an impression cylinder, but it is understood that theteachings herein are not limited to any particular style of apparatusand that equivalent printing apparatus is equally suitable to employ.

For highest quality letterpress printing, certain preliminary steps arerequired in readying the printing apparatus for operation. Makeready isa part of this procedure and, as used herein, involves selectivelyvarying the thickness of packing on various areas of animpressioncylinder, and/or adjusting the height of, or packing beneath,various areas of the face on a printing form so that the impressionpressure under which areas of the cylinder and areas of the face of theprinting form coact during printing is selectively adjusted.

Prior art methods of makeready are extremely time consuming, costly,and, for the most part, do not readily give results comparable tothe'high quality obtained by the practice of this invention. Theyfrequently require the use of messy materials, e. g., sticky ink,various powdery materials, etc., and in addition, individually suffervarious other defects.

Among printers, the oldest known method of makeready, viz., the use ofpaper cutouts, dollies, etc., is the It has also been used to compensatefor pressirregular'ities. While the method is susceptible of producingexcellent results, it is very time-consuming and results obtained areentirely dependent upon the skill and technique of the printer. 1

This invention to a large extent alleviates the burden and expense ofmakeready and provides a new method for accomplishing it expeditiously,accurately, economically and mechanically, all as will be evident asthis description proceeds. By the practice of this invention, makereadyis accomplished with a high degree of fidelity lCC and in a manner whichpermits a number of printing establishments required to print the samesubject matter at various locations to duplicate easily the precisecorrections necessary.

Further provided by this invention are convenient makeready sheetmaterials which mechanically expand in selective fashion when processedaccording to the teachings herein, which have desired strength andtoughness in selectively expanded areas, and which may be stored in theunexpanded state under ordinary atmospheric conditions without loss oftheir desired physical properties. These new sheet materials require nometiculous cutting for makeready use and permit makeready to beaccomplished expeditiously and free of messy components, such as pastes,powders, etc., as required in the prior art. We know of no makereadysheetmaterials of this type which were commercially available prior toour invention.

By utilizing the makeready teachings herein, prints may be made whichhave delicate shadings, dense solids and clean highlights. Such prints,obtainable after only a short makeready time, are especially desired bypublishers of encyclopedias, art magazines, and the like, wheremakeready has become an extremely time-consuming process. The variousmakeready constructions hereof give to printing forms a longer presslife than heretofore experienced.

In describing our invention, we choose to refer specifically tomakeready for graphic arts printing forms, but it will be understoodthat our novel process and sheet materials are also suitable to employin making ready,

or as makeready for, other printing forms. 7

Fundamentally, theoretical explanations aside, to provide appropriatelycorrected impression pressures for highest quality graphic artsprinting, the relative thickness of packing over solid tone areas must,with respect to the thickness of packing over middletone areas, beincreased. Additionally, however, the thickness of packing over theperipheral area of solid'tones generally should be less than that overcentral areas thereof, and further, the thick.- ness of packing overmiddletone areas having a very high density of dots or printing elementsshould be comparatively greater than that packing over middletone areashaving a very low density of dots or printing elements. course, asevident from the above, the relative height of, or packing beneath,areas of solid tone may be raised-or increased relatively to areas ofmiddletone to accomplish also a suitable correction for printing.Highlight or nonprinting areas of a printing form should receive leastpressure in printing and therefore should generally have the leastpacking. 1

Variation of the thickness of packing on an impression cylinder involvesoverlay makeready. Corrective ma.- terial inserted beneath themountingblock on which a printing form rests is underlay makeready;Interlay makeready involves placing corrective material beneath theprinting form, e. g., an electrotype, but above the mounting block onwhich it rests. Adjusting the height of various areas on the face of aprinting form may involve a bump-up process such as hereinafterdescribed. According to our invention, a makeready sheet material havinga flexible selectively-thermoexpansible layer which is resistant tocompression in expanded condition, is inked or printed with the generallikeness of a printing'form, exposed to radiant energy for diiferentialsustained expansion, and finally, placed in registration with a printingform. The processed sheet material essentially provides the amount andkind of makeready correction needed to Figure 2 ,is a diagrammatic,section through a portion of a printing form and an impression cylinderwrapped with our makeready sheet.

Figure 3 is a diagrammatic section through a source of high-intensityradiant energy and a makeready sheet selectively expanded in part.

Figure, 4 is a diagrammatic section through a portion of a printing formand an impression cylinder having a selectively-expanded makeready sheetin registered overlay position.

Figure 5 is a diagrammatic exploded sectional view illustrating twosqueeze rollers, two metal plates, and a laminate comprising a negativeselectively expanded makeready sheet, a printing form, and a positiveselectively. expanded makeready sheet l(here shown slightly outofregister-L1.

Accordingto the preferred embodiment of our process, designated forbrevity as the overlay process, the selectively-thermoexpansible. layeror side of. n r ayyp makeready Sheet non-absorptive of radiant energy,e. g., a sheet such as illustrated in Figure 1 comprising a carrier web20. and a selectively-thermoexpansible layer 21, is first inked orprinted upon with a radiant energy absorptive ink This may beaccomplished in the manner illustrated in Figure 2. t Sheet: 22 with itsheat-sensitive layer 21 outermost is fastened around impression cylinder23 over several layers of packing 24, which provides adequate overallgeneral impression pressure. Printing form 25, e. g., an electrotype,supported onmounting block 26, is inked and the wrapped impressioncylinder rolled thereover. Desirably, the, position of the resultingprinted sheet on cthe impression cylinder is now marked, suitably by.punching a few holesthrough the leading or front edge of the sheet andseveral layers of cylinder. packing, so as to facilitate its subsequentregistration.

After. initial .printing, the makeready sheet is removed from theimpression :cylinder and briefly exposed to uniform and intense radiantenergy. Figure :3 illustrates one way for accomplishing suitableexposure. In this figure, sheet material 22 with inked layer 21 towardhighintensity radiation source27 in elliptical reflector 28, is moved tothe right, as indicated by the arrow, through narrow focused band 29 ofradiant energy. In those areas to the right of band 29, the sheet isillustrated as selectively expanded according to the pattern of infraredabsorption shown as inked thereon. Solid tone printed area 30is greatlyexpanded, while middletone printed areas 31 and 32 of proportionatelyless printing point densityare expanded only to a degree approximatelycommensurate with their tone. Unexpanded printed areas 33, to the leftof the focused band or line 29 have-not yet been exposed. Non-printedareas 34are unexpanded.

In this exposure step, ink on the makeready sheet absorbs radiantenergy, becomes heated, and in turn heats areas of theselectively-thermoexpansible layer of resinous material andpuffing agentadjacent thereto by conduction. These areas soften, the pulling agent inthe sheet is activated inthe soft areas under conditions of heat, andthe gas of the puffing agent produces bubbles in the softened areascausing themyto, swell. The thermoexpanded areas are then allowedto coolandgenerated gas remains entrapped. in the expandedareas of. the layer.Local areas of theprinted sheet which have a high ratio of inkedsurface, .i. e., solid or black tone areas, absorb a greater amountofradiant .energyand cause a greater amount of gas formation by thepuffingagent thanareas where this 'atiois small, e. g., middletone areas. Areasof the sheet not printed, i. e., highlight areas, do not absorb radiantenergy or do so only to a slight. extent insufficient to effectexpansion thereof. Theflresulting .sheet after exposure has .a thicknessrelief corresponding to the tone of the. printing form, being thickestin solid tone areas (and of greatestthickness in the center of suchareas),thinnest '4 i a t in non-printing orhighlight areas, and ofessentially graduated thickness between these extremes.

Conditions of radiant energy exposure are especially detailed in thedisclosure set forth in connection with Example 1. It will be noted thatexposure to intense radiation is brief to prevent char-ring of theselectivelythermoexpansible layer, and that intense and uniformradiation is necessary to achieve high and selective expansion of theheat-sensitive layer before any significant dissipation of heat has achance to take place therethrough. While heat-sensitive, our expansiblelayers are poor conductors of heat.

After exposure, the sheet is returned to the impression cylinder andregistered with the printing form, as for example by matching thepunched holes in the underlying packing and the makereacly sheet. In anideal overlay construction, the makeready sheet is placed beneath two orthree layers of heavy packing paper (each layer being approximately0.006 thick). The sheet preferably is not buried too deeply in thepacking on the impression cylinder inasmuch as the tendency is then toupset desired registration. The outermost layer on an impressioncylinder ready for printing suitably may be a printing blanket or thelike, as is well known in the art. However, the makeready sheet itselfmay be used as the outer layer, if desired.

In Figure 4 a makeready sheet hereof 22 is illustrated in registeredposition beneath one layer (chosen for clarity of illustration) ofpacking 2411 upon impression cylinder 23. A layer of packing 24b ispositioned beneath the makeready sheet. Selectively expanded areas 30,31 and 32 of sheet 22 coact during printing with solid tone area 35 andmiddletone areas 36 and 37, respectively, of printing form 25, mountedon a suitable support 26. Apaper sheet 38 is illustrated receiving theinked image of the printing form.

Our complete overlay makcrcady process may be accomplished in as short aperiod as 10 minutes as compared to prior art processes requiring, inmany cases, an hour or more. One of the largest expense factors aboutmakeready, i. e., printing delays or press down-time, is thereforegreatly reduced.

If desired, overlay-typc sheet'materials processed according to theforegoing may be registered for underlay or interlay makereadyconstructions. In such constructions, the carrier web side of the sheetis positioned next to the underside of the printing formior the mountingblock), and the selectively expanded layer lowermost.

The following examples are illustrative but nonvlimitative of ourinvention. For convenient reference, the various characteristics of thesheet materials of Examples 1 through 7 are tabulated below in Table I.All of the sheet materials of Examples 1 through 7 were processedusingour overlay makeready process, and placed in registration beneathtwo layers of 6 mil (0.006) packing on an impression cylinder. Printingdone on commercial appartus with such makeready constructions gaveprints of exceptionally fine quality. Solid tones, were dense,highlights clean and middletones delicately shaded according tothedensity of printing elements, as desired.

EXAMPLE I 1 Parts by weight Cellulose acetate butyrate Polyvinyl acetatet 90 Plasticizer u 39 Solvent 500 Paste -c- 12.8

The cellulose acetate butyrate'was obtained under the trade name /2Second Butyrate," which is a low viscosity but hard cellulose-derivativethermoplastic resin, having a melting range of approximately 284-338 Fi, an intrinsic viscosity in acetone at 25 C. of approximately 0.66 to0.86, a molecular weight of approximately 30,000. an

acetyl content between approximately 12 to 15 a butyryl content of 35 to39%, a hydroxyl content of 0.5,to 1.2%, a free acidity content ofapproximately 0.03 maximum, and a maximum moisture content ofapproximately 3%.

The polyvinyl acetate was Vinylite AYAT, which has an approximatesoftening point of 187 F., an intrinsic viscosity in cyclohexanone at C.of 0.69, and a specific gravity of 1.18.

The plasticizer was Paraplex G-20, which is a 100% sebacic acid estertype polymeric plasticizer containing no modifying oil. The solvent wasa mixture of 40 parts toluene,9 parts ethanol, and 1 part normalbutanol.

The paste was made by milling the following consti tuents on a paintmill into a uniform blend:

, Parts Puffing agent 2 Plasticizer 2 Solvent 1 The puffing agent,Celogen, was p,p-oxy bis (benzene sulfonyl hyorazrde), which decomposesat raised temperaturesbeginning at approximately 266 F., releasingnitrogen gas. The plasticizer and solvent in the paste were the same asthose constituents in the resinous mass of this example. 1

The components above, other than the paste, were stirred together untila smooth solution was obtained. To this solution was then added thepaste and stirring continued until a uniform blend resulted. About 17additional parts of solvent were then added to the mass to reduce itsviscosity and the blend then coated on 42 pound Minniform paper (ableached Kraft converting paper) marketed by the Minnesota and OntarioPaper Company. A wet coating thickness of approximately 20 mils (0.02)was employed. Some. impregnation ofjthe paper backing resulted. Thecoating was dried for approximately-one half hour at room temperatureand then for approximately ten minutes at 160 F. and finally forapproximately twenty minutes at 225 F. The steps employed to accomplishdrying were for the purpose of removing as completely as possible allsolvent and moisture from the coating. In addition the short heatconditioning treatment of approximately twenty minutes at 225 F. servedto smooth and density the coating and thereby impart increased moistureresistivity to the, sheet. 1

The resulting sheet was inked with the pattern of a printing form usingconventional oil base carbonfpigment printersink. The ink wet the smoothresinous surface uniformly and remained effectively distributed in thepattern of the face of the printing form employed. The inked sheet wasthen briefly subjected to uniform and intense radiant energy. l

The source of radiation employed was a tungsten linefilament lampmounted lineally in a sealed quartz tube; however, equivalent sourcesmay be used. At 230 volts the lamp had a capacity of 650 watts. The tubewas mounted along the. axis of the internal forms of an ellipticalreflector having a focal distance of 0.852inch. The other focal axisof'the reflector was in the open, i. e., outside the boundaries of thereflector. The inked makeready sheet was rapidly passed in front ofthe'reflector in the plane of the external focal axis, with theconcentrated line of radiation thereby being focused on a narrow stripof the printed surface. The width of the line concentration of focusedrays was approximately three-sixteenths of aninch. a Y

The temperature of the radiation source, as measured by an opticalpyrometer, was 2460 Kelvin at an input of 300 volts giving 970volt-amperes. Under these conditions the makeready sheet, resting on aninsulating blanket, was passed twice below the light source at a speedof 80" per minute. IHad the sheet been passed beneath this source at aspeed of approximately 20" per minute, charring of the sheet would haveresulted.

In solid tone areas the sheet expanded to a total thickness ofapproximately 10.7 mils, 3.2 mils above areasof the sheet not expanded.Other areas, such as middletone areas and highlight areas, expanded to adegree commensurate with the darkness of their tone, nonprinting areasremaining unexpanded. For example, in a middletone area of 20% printingelements nonprinting or clear) the sheet expanded to approximately 8.1mils, 0.6 mil above non-expanded areas. The processed sheet, in otherwords, presented a thickness relief corresponding to the tone of theprinting form.

If a source intensity of radiation, i. e., infrared or equivalent, istoo low during processing, insufficient expansion of the sheet results,or the sheet expands in a generally non-selective fashion. If a sourceintensity of radiation is too high, the makeready sheet hereof chars andloses its value as a corrective sheet in printing. For example, at asource temperature of 2310 Kelvin at 250 volts giving 720 volt-amperes,the printed sheet of this example was passed three times through theline focus of radiation at 60 inches per minute. 1 he resultingselectively expanded sheet was barely suitable for use in print} ing.Its pattern of expansion was not as accurate in relief as that patternexhibited by the sheet expanded according to the preferred conditions ofradiation hereinbefore set forth. At a filament temperature of 2700 K.at 375 volts giving 1350 volt-amperes, the sheet of this example waspassed three times at a speed of inches per minute through the linefocus of irradiated rays. Despite the rate at which the sheet wasprocessed, expanded areas were charred. While solid tone areas of thissheet were expanded to approximately 4.5 mils above the 'surfaceof thesheet, they were charred and could not withstand any great printingpressures.

The sheet materials of Examples 2, 3 and 4 were processed using thepreferred conditions of exposure set forth in this example.

The thermosetting resin employed was an epoxy condensation polymer ofepichlorohydrin and bisphenol A commercially available under thedesignation BR- 18774, which consists of 100% solids having an epoxyequivalency of 180 210, and a viscosity at 25 C. of 10,000 to 15,000cps. The solvent was a mixture of 40 parts toluene, 9 parts isopropylalcohol and 1 part normal butyl alcohol.

The ingredients above were added to the solvent in the order listed andstirred until a uniform blend resulted. The blend was then knife-coatedwith an orifice of 0.025 inch upon 42 pound Minniform paper. The coatingwas air-dried at room temperature for approximately onehalf hour,oven-dried for approximately '20 minutes at F. and then'20 minutes at225 F. The raised temperature of drying'advantageously served tocondition the resinous coating so that it became less moisture sensitiveand to efiect curing of the thermosetting resin.

We haveemployed a wide variety of puffing agents in makeready sheetssuch as set forth in the example. An intimate mixture of urea andbiuret, which decomposes at approximately 300 F. releasing ammonia, hasbeen employed. Potassium bisulfite has been employed. Even smallquantities, e. g., on the order of 3% by weight, of

ammonium aluminum alum, which releases. its water of hydration atapproximately 248 F., have been employed,

EXAMPLE 3 Parts by weight Polyvinyl butyral 100 Plasticizer of Example 12O Toluene -4 180 Isopropyl alcohol 120 Puffing agent of Example 1 6 Thepolyvinyl butyral employed here was obtained under the designationButvar B76, which is produced by liydrolyzing polyvinyl acetate topolyvinyl alcohol and reacting the alcohol with butyraldehyde to givepolyvinyl butyral. It has a softening point of 170 F., a hydroxylcontent of approximately 13.0% (calculated aspolyvinyl alcohol) and apolyvinyl acetate content of approximately 2.5%.

The above ingredients were mixed together until a uniform blendresulted. This uniform blend was coated on 42 poundMinniform paper in amanner as set forth'in Example 2, the coating dried to a tack-freeconsistency at room temperature, and thenovendried for'approximately 20minutes at 150 F. and 20 minutes at 225 F.

EXAMPLE 4 Parts by weight Hard polystyrene resin 35 Toluene 65 Pulfingagent of Example l 1 The hard polystyrene resin employed in this examplewas' an unmodified polystyrene sold under the trade name Styron 666.According to tests of the American Society for Testing Materials, it hada tensile strength of 6,000to 7,000 p. s. i. (ASTM D638 49T),an'elongation of 1.5 to 2.0% (ASTM D638-49T), a flexural strength ofbetween 12,000 to 15,000 p. 's. 'i. (ASTM D790-49T), a heat distortionrange of 168 to 175 F.", (ASTM D 648-45T), and a Rockwell hardness ofM68- 80 (ASTM D785-48T). i

To the solvent, toluene, was added the polystyrene polymer in particleform and stirring continued until the polymer was uniformly dissolvedtherein. The puffing agent was crushed to a particle size ofapproximately 1 mil or less and dispersed, i. e., blended thoroughly inthe solution by stirring. AWaring blendor may suitably be employed.

The resulting blend was coated, using anorifice 0.020" thick, upon.90lb. fourdrinier paper commercially available under the trade nameSanfast. A heavy backing is necessarily used with the cxpansibleresin-layer of this example inasmuch as the non-plasticized resin layerof this example exhibits a relatively hightende'ncy to cause curlingwhen coated upon relatively thin light weight backings. After beingapplied to the heavy backing, the resin coat was air ried forapproximately one-half hour at room temperature and then oven-dried for20 minutes at 150 F., followed by 20 minutes at 225 F.

EXAMPLE.

Gram parts'by weight Vinyl. chloride-vinyl acetate copolymer- 1200Plasticizer 4S0 Amyl. acetate 624 Volatile petroleum naphtha .J. 680Puffing agent of Example 1 30 The vinyl chloride-vinyl acetate copolymerwas an mgm. of KOI-I/gm. The naphtha used has a specific gravity (60,"F.=/60f F.) of 0.733 to 0.735..

All ingredients. above except the putting agent were added to a 2-gallon jar half filled with porcelain balls of approximately one-halfinchdiameter. The jar was rolled for about 16 hours to thoroughly mill thecontents, after which the pufiing agent was added and milling continuedfor an additional 2 /2 hours. Milling time and conditions may varydepending upon the type of container employed, the size of hard ballsused, etc.

The organosol mixture thus prepared was knife coated at a thickness ofmils upon a 3-mil thick brass foil, the surface of which had previouslybeen roughened with sandpaper. The coating was dried for 2 minutes at180 F. and fused for 5 minutes at 260 F., a temperature below thedecomposition temperature of the.

pufiing agent.

The resulting sheet was printed and heated to approximately 180"F. asmeasured bya surfa'ce pyrometer at the metal surface. The heated sheetwas then exposed to radiant energy using conditions of actual exposureslightly less severe than those set forth in'Example 1, resulting in theformation. of a high graduated relief pattern in the resinous layer.Preliminary heating of a heat-conductive metal-backed sheet to anambient temper'ature above approximately Fjbut below the decompositionpoint of the pufling agent incorporated thereinis believed to reducelateral dissipation or transfer of. heat in the backing during exposureto radi a nt energy, whereby erratic or poor expansion of the resinouslayer of the sheetis avoided. i

EXAMPLE 6 A flexible non-woven fabric support 4 mils thick, formed byfusing randomly oriented fibers consisting of approximately 40%non-thermoplastic viscose (reget'r erated cellulose) fibers andapproximately'60% thermoplastic cellulose acetate fibers, wasimpregnated with the organosol'resin dispersion of Example 5 using a 3mil orifice. This impregnating coating was air-dried for a few minutesat room temperature, anda second coating knifed thereover using a 20 milorifice. The'structure was then dried for 24 hours at room temperature.

The resinous layer of this sheet contained tiny discrete particlescoherently held together. They could be crumbled from the sheet byrubbing the structure briskly, but under actual conditions in printing;did not flake, split, crack or become displaced. Using conditions ofexposure to radiant energy set forth in Example 1, printed areas of theparticulate layer, i. e'., those inked ar'e'as absorptive of radiantenergy, selectively fused into a tough, continuous phase. Highlightareas or non-inked areas not absorptive of radiant energy remained in anunfused state. Decomposition of the pulling agent took place at a pointslightly above the point at which the particulate resinous layer fused;therefore, generated gas remained entrapped within the layer giving thedesired graduated relief. pattern.

Porous fabric backing members may be impregnated with any suitablematerial prior to coating. Makeready sheets having highly poroussupport. members impregnated as well as coated with our resinous massesmay be inked upon either side and exposed to radiant energy to form anappropriate relief for makeready.

EXAMPLE .7

Gram parts by weight Vinyl chloride-vinyl acetate copolyrner of Example5 .L 50

Adipyl dihydrazide has a melting point of about 350F., and at raisedtemperatures, i. e., temperatures near its melting point, is a highlyeffective curing agent for epoxy resins. it is inert in this resinousmixture at room'temperatures. Instead of adipyl dihydrazide, 2,4-toluenedisulfonamide, malonyl dihydrazide, or other heat-activatible curingagents for epoxy resins may be employed. Malonyl dihydrazide acts notonly as a curing agent for epoxy resins but also as a pufling agent.

The pufling agent used here, available under the name Celogen AZ,releases nitrogen gas on heat decomposition starting at about? 85 F.

The ingredients above were milled together using th method ofcompounding set forth for Example 5, and knife-coated upon a backing ofthe type used for Example 1 with a 17 mil orifice. The coating was driedfor about 6 minutes at room temperature and fused at 275 F. for threeminutes. The uncured epoxy resin in the coating served to plasticize thevinyl resin. I p

This makeready sheet was processed using conditions ofexposure onlyslightly less severe than those employed for the sheet of Example 1.During processing, the heat generated in selected areas absorptive ofradiant energy was 'sufiicientto partially cure those areas of thesheet,

thereby enhancing their expanded strength. Other areas not absorptive ofradiant energy, and not therefore heated, remained uncured. If desiredthe epoxy resin in such areas may be cured by a short heating step justbelow the temperature of decomposition of the pulling agent. In thefollowing table various characteristics, as identified, of the foregoingmakeready sheets are tabulated.

Table I Example 1 t 2 f 3 f 4 I 5 6 7 (1. Thickness of backingin mils(thousandths of an inch).

0. Total mil thickness of unexpanded dry sheet material.

0. Thickness of selectively thermoexpansible layer (ba).

it. Total thickness o sheet material in maximumly expanded areas, i. e..solid tone areas. measured at room temperature after processingaccording to the teachings herein.

a. Differential in thickness between maximumly expanded areas and theinitial thickness of the sheet or unexpanded areas (db).

f. Total mil thickness of processed sheet material in maximurnlyexpanded areas under a pressure of 250 p. s. l. for 15 seconds at roomtemperature.

a. Diflerential in thickness of processed sheet material between maximurnly expanded areas under a pressure of 250 p. s. i. for 15 seconds atroom (tfggerature and the initial thickness of the sheet or unexpandeclareas h. Weight percent of dissolved water in the unexpandedselectivelythttirmo ei pansible layer after conditioning for three daysat 56% R. H. an 75 1. Weight percent of dissolved water in theunexpanded selectivelythedrriogei pansible layer after conditioning forthree days at 93% R. H. an a In the foregoing examples we used solutionor dispersion coating methods to fabricate our sheets; however, othermethods such .as calendering, extruding, etc., may be used. Theimportant requirement is that the resulting coat must be at least about2 mils thick over the entire backing member or carrier web and should beof essentiallyuniform thickness. Any suitable method may be used toaccomplish this result.

Small amounts of various inert fillers and materials, for example,aluminum powder, calcene, silica fines, bentonites, etc., maybe'incorporated in a uniformly dispersed condition in the resinouslayers of our sheets.

Our sheet materials may be characterized as essentially of uniformthickness and as flat-lying in that they remain substantiallyflat'and-resist curling, warping, etc., during. processing. Overlay-typesheets such as those of the foregoing examples are preferably not morethan I under a pressure at least as high as approximately 250 v 10 Iabout 12 mils thick for the reason that more accurate control of thedesiredpacking and of registration on an impression cylinder is possiblewith such sheets.

. The carrier web is dimensionally-stable or planarlystable in that itimparts planar stability, i. e., resistance to curling, warping,stretching, etc., to the makeready sheet. Registration of the sheetmaterial after processing is thereby easily accomplished. In the mostideal sheet structures, the backing member is' between approximately 2and 5 mils in thickness. Other flexible backings than those set forth inthe examples may be employed. For example, non-fibrous films ofglycol-terephthalate polymer v (Mylar), cellulose acetate, silk screens,various metal sheets or foils, various laminates of materials,impregnated materials, etc. are employable. At least one surfaceof thebacking material is preferably of a sufficiently fibrous nature foranchorage of the selectively-thermoexpansible' resinous layer thereto;however, smooth surfaced backing sheetsmay be roughened to secureadhesion or bonding of the resinous layer thereto, as illustrated inExample 5, or an interposing layer of adhesive maybe used to firmly bondthe backing and resinous layer together. i

Preferred overlay-type sheets hereof have backing members characterizedas of low heat conductivity, particularly if compared to theconductivity. of metals, so that lateral diifusibility of heat throughthe backing support from limited localities thereof 'aifected by heat inadjacent portions of the adhered resinous layer during processing isminimized. ,We may, however, as in Example 5, employ thin flexibleheat-conductive metal backing members. Metal backings. inherentlypossess desirable properties of strength and dimensional stability.

Backings are. preferablylight in color for the reason that manydarkcolored backings coated with translucent layers absorb infrared rays. Werealize, however, that dark colored backings maybe used and a highlyreflective or opaque resinous coating employed or a' different range ofradiant energycmployed, to selectively expand the sheet according toselective absorption by a special inkfhaving absorptive powers for theparticular rays employed. This we consider'an equivalent of our inven-'tion. i H 7 Likewise, although in the preferred embodiment our sheetsare printed with inks having'high absorptivity for infrared rays, e. g.,black ink, we may employ other inks having absorptive qualities for adifferent range of radiation than infrared rays and use resinous layersand backings which donot absorb these rays, or which do so only to aslight extent. This, also we consider an equivalent.

The resinous material in our, selectively thermoexpansible layer isusuallypolymeric and must be thermosoftenable as may be noted from theexamples and illustrations hereof. Preferably, at least one hardhydrophobic thermoplastic polymeric material is employed in making up.the; layer Materials having a Shore D Durometer hardness above 40 aregenerally preferred,

but sucha hardnessvalue is somewhat misleading inasmuch assofter-materials whichare thermosetting or' curable to suitable hardnessin processingmay be used. Resinswhich are thermosetting buttemporarilythermoplastic,which areQthermoplastic and .vulcanizable, aswell as others and .iriivariouscombinations-all are employable if inthe; final coat after heat'softening, 'pufiing'and cooling, theselectively"expanded resinous layer is non brittle (particularly ascompared to abietic acid or rosin) and possess'essufiicient hardness,resilient strength and toughness to resist'flattenin'g in use, e. g., tomaintain approximately a '2 mil differential in thickness between (a)fuliyor maximumly expanded areas after 15 seconds p. "s. i. (lbs/in and(b) those areas of the sheet not expanded. Such conditions of time andpressure are believed to closely approximate those encountered undermost actual printing conditions;

Also. employablei together inthe layer are resins. and other componentswhich are incompatible, but which after drying, do not sublimeor'migrate from the'layer.

A coating of non-. compatible resins and other components may be heatedslightly to. improve the dry stability thereof. Preferred selectively.thermoexpansible layers have a uniform smooth fusedappearance, but, asillustrated in, Example ,6, our layers may be comprised of. apluralityof individual particles. 1

Preferably he dry thickness of the selectively thermo expansible layerinmakeready sheets especially designed for overlay use is between,approximately 2 and 7 mils u be as g satas 12 mils, or. gr ater, withsatisfactory results. By dry we mean normally less than, about 3% vola oanic solvent by we h so as. to prevent ckin ots clsq she s nd so as toavo unnecessary s knsss siui'th la e u onsxpansion- A thi kness o atleast 2 mils s ne ded it tel raduat d r ie p rns ar i he ormed- Thinnercoa fail to xpan e ab an even los an q l'fit t e n Qur y rs generallycontain small amounts of orgapiqusually pplymeric; plasticizers fortheir thermoplastic resipous components se the adva taswu planar s ab y,ed of tcadsa y to 9 a d rar aswsl as n some cases iiicreased moistureresistance, imparted to the resulting layer. Plasticizers, however,almost'invariably Somewhat l e na d St en h of a r sinous a er-Accordinglyjthe layer'of such sheets is generally at least about 3 milsthick, and usuallybetween 4 and] mils thick for best results in terms ofmaintaining suitable expanded thickn'essditferentials under psessure'lLayers greater than approximately 12' mils thick are generallyundesirable ,becausee'xpanded areas are apt to bejdis placeable undercompression, and desired high" differentials in thickness areapt tobereduced because of, the greater relative compressibility, of .suchthick coats. This disadvantage of thick coats or layers may be correctedto some extent by incorporatingtherein suitable curing agents orthermosetting resins;

The dispersed, heat-sensitive, normally dormant, putting agent in the,selectively-thermoexpansible' layer re mains therein in a storable,stable condition. It may, in fact, react with the resinous mass, cureit, or even'be a molecular component of a resin,:' so' long'" as'jitretains its requiredability toexpand the layer under conditions of heat.Finely pulverized," uniformly dispersedfparticles of a putting agentfacilitate the formation of a large number of tiny bubbles of cavitiesin. the resinous layer, with a greatnumber of connecting columns ofresin, all of which contributes to .the strength and resiliency ofexpanded areas, as well as to the formation of'wellregulated graduatedreliefpatterns. v i

The amount of putting agent employed may vary depending: upon therelative ability of the agent to expand the sheet under, conditions ofheat employed in processing. A resinous layer may contain as little, asapproximately 1% by weight of a highly efficient puffing agent, e. g.Celogemi but may require up to approximately 30% by weight of a lessefficient agent. Amounts in excess of approximately by weight aregenerally to be avoid ed inasmuch as certain weaknesses are :apt todevelop within thegsheet. Howeveryan inetficient putfingagent whichcontributes to the strength of thesheet may be suitable to employ inhigh concentrations. Preferred puffing agents chemically decompose atraised temperatures to give otfja gas; however, materials. or puffingagents which act by vaporization on heating, as opposed todecomposition, whileinferior, maybe suitable to use.

The preferred temperature range at, which expansion, of r at-Smith makesv s e s cur is we l.

b v m t mper ure-a is be een app o im s y 150 F. and 3509, F.,.but maybe as high as4 50 E, or of, even eonsiderably higher. Expansion atexceedingly was? low temperatures is generally unreliable and notcontrollable; on the other hand, expansion which does not occur untilexceedingly high temperatures, i. e., those for example over about 450or 500 F., are attained creates problems with respect to suitableexposure conditions for processing as well as with respect to obtainingsuitable graduated relief patterns. l l

The temperature at which our resinous masses soften and the temperatureat which a polling agent incorporated therein gives off gas shouldgenerally be within approximately the range of 75 F. of each other,although for some less critical combinations, a temperature differenceas great as about F., or even greater, has been found useful.,Generally, however, it has been found that if a pufiing agent generatesgas at a temperature too far below that at which a resinous layersoftens, control of expansion becomes difficult and desired graduatedreliefpatterns are not easily obtained. If, on the other hand, theputting agent releases gas only at temperatures greatly above those atwhich the resinous material softens, dimculty arises with respect tomaintaining the released gas within the softened resinous layer so as toexpand the same. The faults of extremes are easily avoided if materialsare selected with a view toward maintaining the activation temperaturefor the putfing agent reason ably close to the softening temperature ofthe resinous layer;

The selectively-thermoexpansible layer. of our sheets has a prolongedshelf life and may be characterized as hydmphobiclin thatit resistsimbibition of water or mois ture to an extent that it does not containsufiicient dissolved water, even after being stored under atmosphericconditions, to interfere greatly with thegaining of high, graduated,tough and sturdy relief patterns when it is. later exposed to radiantenergy during processing'fas: taught herein. The foregoing definitionfor the required, hydrophobic nature of our heatexpansible layers,isfai' more accurate than quantitative figures on their maximumpermissible moisture content; although, wheni us ing such a standard,the heat-expansiblc layer of our sheets does not contain, even whenexposed for lengthy periods to especially adverse conditions oftemperature and moisture, more dissolved water than from 0 upto 4% byweight. Expansible layers which contain more than about 4% Watcr'byweight give unreliable results in expansion and erratic relief patterns,frequently of greater thickness in middletone than solid tone areas,when made heat-sensitive and processed as taught herein. In Table Iqualitative data as to the dissolved moisture content in theselectivelyethermoexpansible layers of the foregoing examples is setforth. Particulan note should btakcn of thoselow values obtained whenthe articles of the examples were stored under high humidity condi-.

tions such as might be encountered in summer months.

The surface of our selectively expansible layers may be characterized aslyophilic or organophilic in that it accepts conventional printing inksreadily and is not deleteriously affected thereby, even though theprinting inks contain oils and the like. The ink receptive nature of ourselectively expansiblelayers may be appreciated when it is realizedthat, areas inked upon our sheets are not significantly altered in shapeby such phenomenon as surface tension which may cause an inked area topullup into globules. Instead the ink wets the resin surface and remainsin position upon the sheet substantially, as it was originally applied.Cur, sheets; after. processing do not flake, split, crack, becomepulverized, or exhibit cold flow under conditions of use. We believethat the selective and. proportionate resiliency, toughness, andstrength of our. selectively ex.--

pended layers, including their ability to. resist. crushing anddisplacement as Well as flattening compressive forces such as areencountered in printing, i. e., presspoundingj? accounts in a largemeasure for the, especially,v fine.

13 printing results obtained when our sheets are employed as taughtherein.

According to another embodiment of this invention, there is provided anovel process and also makeready sheet materials for bumping-up ordistorting electrotypes, photoengravings and the like in a very accuratemanner for appropriate impression pressure corrections in printing. In abump-up plate treatment process, a positive paper cutout relief sheetwith dark tones raised is registered under a printing form, e. g., anelectrotype, and a negative paper cutout, i. e., one with highlighttones raised in relief, is registered over the electrotype. Thislaminate is then placed between rigid metal plates and the resultinglaminate passed between squeeze rollers, which action deforms theelectrotype, raising dark tones relatively to highlights. The sodistorted electrotype is shaved smooth on its back surface before thenegative sheet is removed, and thereafter, is mounted on a suitable basefor printing.

Example 8 illustrates this specialized embodiment of our invention. Aswill be evident, the general characteristics of overlay sheets above setforth are also applicable 7 to sheets of this embodiment of ourinvention. The sheets of this embodiment, however, possess a greaterstrength in expanded areas.

EXAMPLE 8 Parts by weight Epoxy thermosetting resin of Example 2 6O2,4-toluene disulfonamide (Epoxy curing agent) 8 N-(3diethylaminopropyl) phthalimide salicylate (Activator for epoxy curingagent) 0.7 Vinyl chloride-vinyl acetate copolymer of Example 80 Amylacetate 80 Naphtha of Example 5 60 p-Diphenyldiazonium fiuoborate(puffing agent) 4 For the positive sheet, the above ingredients weremilled together to form a uniform dispersion by following the method ofcompounding set forth in Example 5.

For, the negative sheet, the same ingredients, quantities and processwere used except that 2 parts by weight of activated carbon black(Carbolac #2") were added to the mixture about 1 /2 hours before millingwas termi nated. Instead of using a pigment absorptive of radiantenergy, we may use a radiation-absorbent backing or carrier web with atransparent coating and thereby attain an equivalent sheet.

Each dispersion was then knife-coated on a separate carrier web of thetype used in Example 1 with 18 mil orifices. be used. The coatings weredried minutes at room temperature and 15 minutes at 150 F. 'Thedriedcoatings remained in an unfused state; however, the vinylchloride-vinyl acetate copolymer particles in the dried layer wereswelled by what appeared to be a plasticizing action on the part of theuncured epoxy resinin the coating, and the swelled resin particlesseemed to be bonded to each other by the epoxy constituent in ,thelayer. The dried sheet was about 8.5 mils thick, 3.5 mils of which wasbacking.

The dry positive sheet was inked with an impression of the electrotypeto be bumped. Black ink pigmented with carbon-black was employed. Thenegativesh'eet was inked also with an impression of the electrotype butOther backings as discussed hereinbefore may in this case a radiationreflecting or non-absorbing ink was used. Silver ink having a reflectivesilver or aluminum pigment is satisfactory. Each sheet was then exposedto brief, intense and uniform radiation. Suitably, conditions onlyslightly less severe than those described in Example 1 are employed. Theprocessed sheets of this example in max'imumly expanded areas were 14.5mils thick, 3.5 mils of which was backing, and these areas supportedpressures of about 100 p. s. i. for 15 seconds remaining at least about5 mils above areas not expanded. No oven curing was necessary to achievesuch strength 14 I r in the selectively expanded layers of this example,but an oven curing step may be used if desired.

The p-diphenyldiazoniurn fiuoborate functioned during exposure of thissheet not only as a pulling agent but also as a curing agent for theepoxy resin in those selected areas heated. Other such agents arep-aminodiphenyldiazonium fiuoborate, p-toluene diazonium fluoborate,etc.

Referring now to Figure 5 for illustration, the positive sheet 39, inkedwith radiant energy absorptive ink 40 and 41, increased in thickness inthose areas, the greatest increase taking place in solid tone area 40.The negative sheet 42, inked withradiant energy reflective ink 43 and44, increased in thickness in non-inked areas 45 and 46, and exhibitedthe greatest increase in area 45 on which no reflective ink was printed.The hard and tough cured sheets were each in relief form; however, therelief of the negative sheet 42 was the reverse of that of the positivesheet 39. The positive sheet 39 was then registered underneath theelectrotype 47, and the negative sheet 42 registered above theelectrotype. This laminate was then placed between rigid metal plates 53and 54 and the resulting laminate passed between squeeze rollers 48 and49. By this process, the electrotype was distorted, i. e., bumped, inextremely accurate detail. Solid tone area 50 was raised relatively tohighlight areas 51. Likewise middletone area 52 was raised relatively tohighlight areas 51 but was not raised to the same relative degree thatthe solid tone area was raised. The electrotype was, in other words,given a relief distortion. The positive sheet was then removed, the backof the electrotype was leveled, i. e., shaved smooth, and the negativesheet removed. Prints made using this treated electrotype in suitablewell-known printing arrangement were of the exceptionally fine qualityaforediscussed.

The resistance to moisture imbition of the sheet materials of thisexample is as follows: In a test for 3 days at 56% R. H. and 75 F., aswell as in a test for 3 days at 93% R. H. and F., the selectivelythermoexpansible layers in each case contained less than 0.5% by weightdissolved water.

Great strength is required in the expanded portions of these positiveand negative sheets. The strength of the expanded areas, usually cured,is sufficient to support at least 1,000 p. s. i. for 15 seconds andstill remain at least more than 2 mils and generally at leastapproximately 5 mils above the unexpanded portions of the sheet. Thesesheets therefore, are the more unusual when it is realized that suchstrength is gained in vesicular expanded portions. While these sheetsmay also be used as overlaytype makeready sheets, they frequentlypossess more than the desired strength for usual overlay makereadyrequirements.

Our negative sheets, i. e., sheets hereof which are absorptive ofradiant energy and are processed using refiective inks to mask out areasnot to be expanded, may be used also in a bump-up process without thepositive sheet, if desired. In such a process, the negative sheet isprinted with the pattern of the electrotype using a reflective ink, andthereafter, it is exposed to radiation, as herein taught, and registeredover the electrotype. Next, pressure is applied over all points or areasof the back surface of the electrotype to distort it toward andaccording to the relief of the negative sheet. The back surface of thebumped up electrotype is then shaved smooth and the resulting correctedelectrotype is ready for printing.

In another embodiment of our invention, both sides of a carrier web arecoated with a selectively-thermoexpansible layer. To selectively expandboth sides of such a sheet, the following procedure may be followed:

A smooth-outer cover, preferably with a hard glazed surface, is first.wrapped around an impression cylinder' and printed upon. Adouble-coated makeready sheet then is wrapped around the impressioncylinder over the aforementioned printed outer cover and the outsidesurface of the makeready sheet printed upon. During the second printingstep, the mirror image of the printing form is printed by offset uponthe side of the makeready sheet in contact with the originally printedglazed wrapping. Each side of the makeready sheet is then exposed toradiant energy to expand the same, and the expanded sheet placed inregistration as desired.

A novel method for gaining registration of overlay makeready usingrelatively thin translucent sheets such as the one of Example 1 hereof,is as follows: A plain sheet of paper is wrapped around an impressioncylinder, printed with an impression of a printing form, marked forsubsequent registration, and removed from the cylinder. The translucentmakeready sheet is. then printed with an impression of the printingform,'exposed to radiant energy, adhesively securedover the previouslyprinted sheet of paper in registration with theprint thereon, and. thewhole structure registered on-the impression cylinder, using the.

indicia markings on the plain sheet ofpaper.

For linotype printing, it is sometimes desired to increase the packingthickness over certain lines so as to obtain appropriate ink transfer topaper being printed. When using our makeready sheet materialnon-absorptive of radiant energy to accomplish this, one first marks orshades various selected areas of the sheet material with radiant energyabsorptive ink or pencil according. to the desiderata for increasedthickness over various lines or areas of a linotype printing'form.Suitably, markings or shadings of differentinfrared-absorptive qualitiesmay be made by using various pencils, inks, crayons, etc., each withdifferent infrared-absorptive qualities, or-by applying black ink or thelikein various shades or density over various lines or areas -of oursheet material. The 'somarked sheet is then exposed and expandsselectively accordingto the infrared absorptivity-of the marked areas.

'It is then'registered appropriately so as tocooperate with a linotypeform in printing.

Makeready sheets hereof may also be used in making novel sandwichprinting form constructions. One such construction is that gained byregistering a selectively expanded makeready sheet, e. g., apositive-type or overlay-type makeready sheet as above set forth,beneath an electrotype, or the like, and adhesively bondingthe twotogether. The back side of the electrotype-may be shaved down so thatthe electrotype itself is extremely thin. A thin sheet of metalof-uniform thickness may be adhesively secured to the bottom side ofthe'structure, i. e., beneath the selectively thermoexpandedlayer of theregistered makeready sheet, to contribute to the strength of the wholestructure, if desired. Another sandwich type construction results if anelectrotype, or the like, which suitably may be shaved thin, is pressedinto a coating of a .heat-hardenable, resinous adhesive on auniformmetalbackingby using a negative type makeready sheet, as above described, inregister over the electrotype. The negative sheet, selectively expandedin highlight areas, will deform the thin electrotype' into thc adhesivelayer when pressure is appliedthereover. The heat-hardenable resinousadhesive may substantially simultaneously be activated to hold the platein deformed condition. v

A selectively thermoexpansible layer, as well as the backing, for ourmakeready sheets may be formedfrom a wide variety of materials. Becausenewpolymeric hydrophobic resinousmaterials and new puflingor blowingagents are continually being developed and marketed, it is impossible tocatalogue all components useful in a heatsensitive layer. Further such acatalogue by specific chemical-names would be misleading in that .ourinvention relating to sheet materialsdoes not lie in any specific ;touse new materials which may become available, it will 15 .be a simpleexpedient, after studying the foregoing, to make routine tests and toutilize available knowledge in the light of this specification todetermine whether the new materials are suitable. Good judgment willnecessarily be exercised but it is safe to assume that no one willwishto make and process a useless sheet material or will be misled bythe foregoing into making and processing worthless articles using newmaterials and ingredients which may become available.

We are aware ofprior art patents teaching sheet mate- 'rials which arelight-sensitive or photosensitive and are useful in makingphotographic-type images. These patcats are unrelated to makeready forletterpress printing. In general, it may be noted that the sheetmaterials of these patents have thin hydrophilic, even water-soluble,layers which are not'designed to give high, graduated, tough and sturdyrelief patterns upon exposure to radiant energy as taught herein.

What is claimed is as follows:

1. A fiexible, flat-lying, unitary sheet material of essentially uniformthickness adapted for makeready in letterpress printing by aprocessinvolving differential sas tained expansion, said sheet materialcomprising a flexible, planarly-stable, carrier web, and, on at leastone side thereof, a flexible, selectively-thermoexpansible,ink-receptive, hydrophobic layer comprising a hydrophobic, at leasttemporarily thermosoftenable, resinous material and, uniformlydistributed therethrough, a normally-dormant, heat-sensitive,pufiing'agent activatible at a temperature well above normal roomtemperature to expand said layer under conditions of heat, said puffingagent being present in an amount sufficient to provide on rapid andcomplete heat-activation of said layer an increase of at least 2 mils inthe thickness thereof, and said layer being hardenable in expandedcondition to an extent sufficient to support pressures at least on theorder of 250 p. s. i. for about 15 seconds while maintaining areas ofmaximum expansion at least approximately 2 mils greater than the initialthickness thereof.

2. The article of claim 1 in which the selectively-thermoexpansiblelayer contains a thermosetting resin.

3. The article of claim 2 in which the selectivelythermoexpansible layercontains a curing agent for said thermosetting resin.

4. The article of claim 1 in which the selectively thermoexpansiblelayer is at least about 3 mils thick and contains an organicplasticizer.

5. The article of claim 1 in which the selectivelythermoexpansible layercontains a material absorptive of radiant energy.

6. A flexible, flat-lying unitary sheet material of essentially uniformthickness adapted for makeready in letterpress printing by a processinvolving differential sustained expansion, said sheet materialcomprising a flexible, planarly-stable, carrier web, and, on at leastone side thereof, a flexible, selectively-thermoexpansible,ink-receptive, hydrophobic layer at least 2 mils thick and comprising ahydrophobic thermoplastic resin, a thermosetting resin and, uniformlydistributed through said resins, a normallydormant, heat'sensitive,puffing agent activatible at a temperature well above normal roomtemperature to expand said layer under conditions of heat, said pulfingagent being present in an amount suflicient to provide on rapid andcomplete heat-activation of said layer an increase of at least'2 mils inthe thickness thereof, and said layer being hardenable in expandedcondition to an extent sufficient to support pressures at least on theorder of 250 p. s. i. for 15 seconds while maintaining areas of maximumexpansion at least approximately 2 mils above the initial thicknessthereof.

7. The article of claim 6 in which the selectively- -thermoexpansiblelayer contains a curingagent for the thermoset-ting resin.

8. A flexible, fiat-lying, unitary sheet material of essentially mniformthickness adapted for makeready in 17 letterpress printing, said sheetmaterial being characterized by an ability to expand in selected areasto present a relief according to a pattern inked thereon with ink highlyabsorptive of radiant energy, said sheet being sufficiently lessabsorptive of said radiant energy so that, upon exposure of said sheetafter inking to brief, intense, and uniform radiant energy only thoseportions inked will expand commensurately with the amount of inkingplaced thereon to present a relief pattern thickest in solidly inkedareas and thinnest in non-inked areas, and of graduated thickness inother areas approximately according to the density of ink thereon, saidsheet comprising: a

flexible, planarly-stable, carrier web of low heat conductivity, and aflexible, selectively-thermoexpansible, inkreceptive, hydrophobic layeron at least one side of said carrier web, said layer being at least 2mils thick and comprising a hydrophobic thermoplastic resin, athermosetting resin and, uniformly distributed through said resins, anormally-dormant, heat-sensitive, puffing agent activatible at atemperature well above normal room temperature to expand said layerunder conditions of heat, said putting agent being present in an amountsufficient to provide on rapid and complete heat-activation of saidlayer an increase of at least 2 mils in the thickness thereof, and saidlayer being hardenable in expanded condition to an extent suflicient tosupport pressures at least on the order of 250 p. s. i. for 15 secondswhile maintaining areas of maximum expansion at least approximately 2mils above the initial thickness thereof.

9. The article of claim 8 in which the selectivelythermoexpansible layercontains a curing agent for the thermosetting resin.

. 10. A fiexile, flat-lying, unitary sheet material of essentiailyuniform thickness adapted for makeready in letterpress printing by aprocess involving differential sustained expansion, said sheet materialcomprising a flexible, planarly-stable, carrier Web, and, on each sidethereof, a flexible, selectively-thermoexpansible, ink-receptive,hydrophobic layer comprising a hydrophobic, at least temporarilythermosoft'enable, resinous material and, uniformly distributedtherethrough, a normallydormant, heat-sensitive, puffing agentactiyatible at a temperature well-above normal room temperature toexpand said layer under conditions of heat.

11. In a process of makeready for letterpress printing, the step ofbriefly exposing a makeready sheet comprising a flexible,selectively-thermoexpansible layer, and having a differentiallyradiation-absorptive makeready pattern thereon, to uniform and intenseradiant energy differentially absorptive by elements of said pattern toprovide a heat pattern sufficient to expand said layer selectively.

12. In a process of makeready for letterpress printing, the step ofbriefly exposing a makeready sheet nonabsorptive of radiant energycomprising a flexible, selectively-thermoexpansible layer, andhave amakeready pattern thereon of radiant energy absorptive elements, touniform and intense radiant energy suflicient to expand the layer inselected areas in heat-conductive association with the radiant energyabsorptive elements.

13. In a process of makeready for letterpress printing, the step ofbriefly exposing a makeready sheet absorptive of radiant energycomprising a flexible, selectively-thermoexpansible layer, and having amakeready pattern thereon of radiant energy reflective elements, touniform and intense radiant energy sufiicient to expand said layer inselected areas absorptive of radiant energy.

14. A process of makeready for letterpress printing including the stepsof inking a diiferentially radiation-absorptive pattern upon a makereadysheet comprising a flexible, ink-receptive, selectively-thermoexpansiblelayer, and briefly exposing said inked makeready sheet to uniform andintense radiant energy differentially absorptive by elements of saidpattern to provide a heat patern sufficient to expand said layerselectively.

15. A process of makeready for letterpress printing comprising (1)inking a differentially radiation-absorptive pattern upon a makereadysheet comprising a uniform, flexible carrier web of low heatconductivity, and, firmly bonded thereto, an ink-receptive,heat-sensitive, coating of uniform thickness comprising athermosoftening, resinous material containing, uniformly distributedtherethrough, a heat-sensitive, pufiing agent, and (2) briefly exposingsaid inked sheet to uniform and intense radiant energy differentiallyabsorptive by elements of said pattern to provide a heat patternsuflicient to selectively expand said sheet, said expanded sheetpossessing sufficient strength and toughness in fully expanded areas tomaintain at least a thickness variation of approximately 2 mils under apressure at least as high as approximately 250 p. s. i.

16. A process of makeready for letterpress printing comprising (1)inking a pattern with a radiant energy absorptive ink upon a makereadysheet substantially nonabsorptive of radiant energy and comprising athermosoftenable resinous material having a heat-sensitive puffing agentuniformly distributed therein, and (2) briefly exposing the inkedpattern of said makeready sheet to uniform and intense radiant energysuflicient to heat and expand said sheet in selected areas in heatconductive association with said radiant energy absorptive ink.

17. A process of makeready for letterpress printing comprising (1)inking a pattern with radiant energy reflective ink upon a makereadysheet absorptive of radiant energy and comprising a thermosoftenableresinous material having a heat-sensitive pufling agent uniformlydistributed therein, and (2) briefly exposing the inked makeready sheetto uniform and intense radiant energy sufficient to heat and expand saidsheet in selected areas absorptive of radiant energy.

18. A process of makeready for letterpress printing comprising (1)inking a makeready pattern upon a flexible, selectively-thermoexpansiblelayer of a makeready sheet to provide differential radiationabsorptivity, said layer containing a resinous material and a pufiingagent, (2) raising said inked makeready sheet to an ambient temperatureabove room temperature but below the activation temperature for saidpuifiing agent, and then, (3) briefly exposing said inked layer touniform and intense radiant energy differentially absorptive by elementsof said pattern to provide a heat pattern sufiicientto expand said layerselectively.

19. A process of makeready for letterpress printing comprising 1)placing a makeready pattern on a flexible, selectively-thermoexpansiblelayer containing a resinous material and a pufiing agent to providedifferential radiation absorptivity, (2) briefly exposing said layer touniform and intense radiant energy to provide, according to saidmakeready pattern, a heat pattern sufficient to expand said layerselectively, and '(3) registering said 'selectively expanded layer witha printing form.

20. A process of makeready for letterpress printing comprising (1)inking a printing form makeready pattern reflective of radiant energyupon a flexible, ink-receptive, selectively-thermoexpansible layerabsorptive of radiant energy, said layer containing a resinous material,a material absorptive of radiant energy and a pufling agent, (2) brieflyexposing said inked layer to uniform and intense radiant energysuflicient to heat and expand said layer in selected areas which absorbradiant energy, said layer being formed so as to be sufliciently hardand tough in selectively expanded areas to maintain .maximumly expandedareas at least 2 mils greater than the initial thickness thereof whileunder a pressure on the order of 1000 p. s. i. for about 15 seconds, (3)registering said selectively expanded layer over the printing surface ofsaid printing form, and (4) applying pressure. over areas of the back ofsaid printing form so as t'o t9 i accord ng to. the relief; ofsaid-registe ed sel tixe y exp nded ma ere dy shee A Process of. k dy re e press printing eoma s ns (L). k ng a Pa r a pr n ing form withradiant nergy. abs rptive. ink up n. a p ti makere dy sheet substan lyonbsor tive of radiant energy an comprising an ink-receptive,selectively-.thermoexpansible layer. qant inin the m so tening hadenable resinous materi ls a sh ng agent, (2.) nk g pattern of hep im nsform wit r ian energy r tive ink up n a esa ivefm kere yshe t' f a o stu on. su h. as descr be in. s p (1.1 b co t n ng a r di n energyabsorpti m t r al n. uni orm; e teond e ive ass iationtherewith, (3)brieflyv exposing each sheet to uniformand intense radiant energysuflicient to. selectively expand the layers thereof in areas affectedby heat, generated, from absorbed radiant energy, saidselectivelyexpanded layers being formed, so as to be sufligiently harand. t gh. o'maiatain maa mum y xp nded ar as at least 2 mi s g t h n.the initial hickn ss hereof hile under a pressure on, he or er of .0.01?..$.. i. fo about 1 5seoonds, (4.) registering saidselectively-expanded positive sheet below said printing form and; saidselectively-expanded negative. sheet above said printing form, and,(5,), applying pressure over, all areas of said, laminate so as to;distort said printing form by raising solid tone areas and. depressinghighlight areas.

22. A flexible, flat-lying, unitary sheet material of essentially.uniform thickness; adapted for makercady in letterpress printingby aprocessinvolving diiferential sustained expansion, said sheet materialcomprising, aflexible, planarly-stable, carrier web, and, on at leastone. side he eo a flexib e e et e y-the m xn ns bl inkeFeP Y hydropho cyer a e st 2 mi e thick and comprising a hydrophobic, at, leasttemporarily thermosoftenable, tough, resinous material and, uniformlydis tributedtherethrough, a multitude of finepartijcles of anormally-dormant, heat-sensitive, pufiing agent activatible'at atemperature well above normal room temperature to produce a gas as .aresult of'chemical decomposition and; thereby expand said layer underconditions of'heat, said puffing agent being present in an amountsufiicient to provide on rapid and: complete heat activation of saidlayer-an increase of atleast 2 mils in the thickness thereof,

and said layer being hardenable in expanded condition. to an extent tosupport pressures at least on the order of-250p. s; i. for about 1-5seconds while maintaining areas of maximum expansion at leastapproximately 2 milsgreater than the initial thickness thereof. I

23. A flexible, fiat-lying, unitary sheet material: of essentiallyuniform thickness adapted; for makeready in letterpress printing by -aprocessinvolving differential sustainedexpansion, saidsheet materialcomprisinga flexible,

plamrly-stable, carrier web, and, on at least one side thereof, aflexible, selectively-thermoexpansible, .inloreceptive, hydrophobic, atleast: temporarily-thermosoftenable layer at-least 2' mils. thickandcomprising a hydrophobic thermoplastic resin, a thermosetting resin,aheata t a b e atin ag nt f r; said thermosettingn; un o mly d r uted hru h said; ay r, a multitude of fine particles of a normally-dormant,heat-sensitive, puffing agent activatibleatatemperature well above.normal room mperature t p odu a ses as a result: of chemicaldecomposition. and. thereby e p a d layer under eondi ions of. bean.said putfing agent being, present in an amount suliieient. to provide.on rapid and complete heat activation .of said layer an increase of atl'east 2 mils in the thickness, thereof, and said layer being hardenablcin expanded conditionI to an extent to support pressures at, east on theorder of 250 p. s. i. for about 15 seconds while, mainta ning areas ofmaximum expansion at least approximately 2 mils greater than the initialthickness thereof.

24. The sheet material of claim 23 wherein the heatsensitive puflingagent is activated to produce a gas within approximately 150 F, of thethermosoftening tempera ture of the selectively-thermoexpansible layer.

it a 25. The sheet material of claim 24 wherein the carrier web is oflow heat conductivity.

26;. The sheet material of claim 23 wherein theselectively-.thermoexpansible layer contains. a material which absorbsradiant energy, said sheet material being further eharaetgerized in thatits layer is hardenable in expanded condition toan extentto supportpressures at least on the order of H p. s. i. for about 15 seconds whilemaintaining areas of maximum expansion at least approximately 2 mile,greater than the initial thickness thereof.

27. A flexible, flat-lying, unitary sheet material of essentiallyuniform thickness adapted for makeready in letterpress printing by aprocess involving dificrential sustainedexpansion, said sheet materialcomprising a flexible, planarly-stable, carrier web at least about 2mils. thick and of low heat conductivity, and, on at least one sidethereof, a flexible, selectively-thermoexpansible, inkreceptive,hydrophobic, at least temporarily thermosoftenable layer haying auniform surface. characteristic, said layer beingat least 2 mils thickand comprising a hydrophobic thermoplastic resin, a thermosetting resin,0. heatactiyatible curing agent for said thermo-setting resin, and,uniformly distributed through said layer, a multitude of fine particlesof a normally-dormant, heat-sensitive, puffing agent activatible at atemperature well above normal room temperature, and within approximatelyF. of the thermosoftening temperature, of said layer, to pro duce a gasas a result of chemical decomposition and thereby cause, expansion ofsaid layer under conditions of heat, said puffing agent being present inan amount sufficient to provide on rapidand complete heat activation ofsaid layer an, increase of at least 2 mils in the thickness thereof, andsaid. layer being hardenable in ex panded conditionto anextent tosupport pressures at least on t he order of 250 p. s. i. for about 15seconds while maintaining areas ofmaximum expansion at least approximately 2 mil's g reater than the initial thickness thereof.

28. The sheet material of claim 27 wherein the puffing agent is presentin an amount between about 1 and 10 percent by weight of; theselectively-thermoexpansible. layer.

29; The, sheet material of claim 28 wherein theselectively-thermoexpansible layer contains a material which absorbsradiant energy, said sheet, material being further characterizedin; thatitslayer is hardenable in expanded condition to an extent to supportpressures at least on the order; of 1000 p. s. i. for about 15secondswhile maintaining areas of maximum expansion at leastapproximately 2' mils greater than the initial thickness thereof.

No references cited.

U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 2,825,282 James BF er en et al. March 4, 1958 It is herebycertified that error appears .in the printed specification of the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 13, line 73, for "100 p. s. i." read 1000 p. s. i. column 14,line 36, for "imbition' read imbibition column 17; line 33, forhileicile" read flexible line 56, for "have" read having ---e; line '74,for "pattern" read pattern Signed and sealed this 27th day of 1958.

(SEAL) Attest: KARL HO AXLINE ROBERT'C. WATSON Attesting OfficerComnissioner of Patents

